Cohorts D and E will include patients with hormone receptor-positive and HER2 non-overexpressing breast cancer who will receive neoadjuvant chemotherapy. For patients in these Cohorts D and E, WT1 ASCI/placebo (placebo applicable only for Cohort E patients) will be administered on Day 14 of each three-weekly cycle of chemotherapy. Neoadjuvant chemotherapy in Cohorts D and E will consist either 1) if 6 doses of WT1 ASCI/placebo: 6 cycle-treatment chemotherapy regimens consist of 6, three-weekly cycles of anthracycline/taxane-based therapy, or 2) if 8 doses of WT1 ASCI/placebo: 8 cycle-treatment regimens consisting of 4 three-weekly cycles of anthracycline-based therapy followed by 4 three-weekly taxane administrations without trastuzumab. Enrolment in Cohort E will be conditional on the absence of a safety signal and on the adequate induction of an immune response by the WT1 ASCI in Cohort D (defined as >= 40% response rate based on post-Dose 4 anti-WT1 antibody responses in at least six patients). If this criterion is met, 60 patients (40 receiving WT1 ASCI and 20 placebo) with identical eligibility criteria will be enrolled into Cohort E. In case no adequate safety and/or immunogenicity will be obtained in Cohort D, recruitment in Cohort E will not be initiated.